Z. anorg. allg. Chem. 624 (1998) 823±829

Zeitschrift fuÈ r anorganischeund allgemeine Chemie

Johann Ambrosius Barth 1998

Protonation and Hydrogen Atom Abstraction Reactions in the Synthesisof the [HP7M(CO)3]2± Ions (M = Cr, W)

Scott Charles, Janet A. Danis, Sundeep P. Mattamana, James C. Fettinger, and Bryan W. Eichhorn*

College Park, Maryland/U.S.A., Department of Chemistry and Biochemistry, University of Maryland

Received October 14th, 1997.

Abstract. Ethylenediamine (en) solutions of [P7M(CO)3]3±

(M = Cr, W) react with weak acids to give [HP7M(CO)3]2±

ions where M = Cr (4 a) and W (4 b) in high yields. Competi-tion studies with known acids revealed a pKa range for 4 b inDMSO of 17.9 to 22.6. The [P7M(CO)3]3± complexes also re-act with one-half equivalent of I2 to give 4 through an oxida-tion/hydrogen atom abstraction process. Labeling studiesshow that the abstracted hydrogen originates from the[K(2,2,2-crypt)]+ ions or from the solvent (DMSO-d6) inthe absence of [K(2,2,2-crypt)]+ or other good hydrogenatom donors. In the solid state, the ions have no crystallo-graphic symmetry but in solution they show virtual Cs sym-

metry (31P NMR spectroscopy) due to an intramolecularwagging process. Crystallographic data for [K(2,2,2-crypt)]2[HP7W(CO)3]: triclinic, P 1, a = 10.9709(8) AÊ , b =13.9116(10) AÊ , c = 19.6400(14) AÊ , α = 92.435(6)°, b =93.856(6)°, c = 108.413(6)°, V = 2831.2(4) AÊ 3, Z = 2, R(F) =7.65%, R(wF2) = 14.17% for all 7400 reflections. For[K(2,2,2-crypt)]2[HP7Cr(CO)3]: triclinic, P 1, a = 12.000(3) AÊ ,b = 14.795(3) AÊ , c = 17.421(4) AÊ , α = 93.01(2)°, b = 93.79(2)°,c = 110.72(2)°, V = 2877(2) AÊ 3, Z = 2.

Keywords: Metallated Zintl ion; radical hydrogen abstrac-tion; phosphane

Protonierung und Wasserstoffatom-Abstraktions-Reaktionen bei der Synthesevon [HP7M(CO)3]2±-Ionen (M = Cr, W)

InhaltsuÈ bersicht. Ethylendiamin(en)-LoÈ sungen von [P7M(CO)3]3±

(M = Cr, W) reagieren mit schwachen SaÈuren unter Bildungvon [HP7M(CO)3]2±-Ionen (M = Cr (4 a) und W (4 b)) in ho-hen Ausbeuten. Vergleichende Untersuchungen mit bekann-ten SaÈuren zeigen einen pKa-Bereich fuÈ r 4 b in DMSO von17,9 bis 22,6. Die [P7M(CO)3]3±-Komplexe reagieren auchmit einem halben Øquivalent I2 zu 4 durch einen Oxi-dations/Wasserstoffabstraktions-Prozeû. Markierungsexperi-mente zeigen, daû das abstrahierte Wasserstoffatom von[K(2,2,2-crypt)]+-Ionen stammt bzw. vom LoÈ sungsmittel(DMSO-d6) bei Abwesenheit von [K(2,2,2-crypt)]+ oder vonanderen guten Wasserstoffatom-Donatoren. Im festen Zu-

stand haben die Ionen keine kristallographische Symmetrie,hingegen zeigen sie in LoÈ sung etwa Cs-Symmetrie (31P-NMR-spektroskopisch) aufgrund eines intramolekularen¹Waggingª-Prozesses. Die kristallographischen Daten fuÈ r[K(2,2,2-crypt)]2[HP7W(CO)3] sind: triklin, P 1, a =10,9709(8) AÊ , b = 13,9116(10) AÊ , c = 19,6400(14) AÊ , α =92,435(6)°, b = 93,856(6)°, c = 108,413(6)°, V = 2831,2(4) AÊ 3,Z = 2, R(F) = 7,65%, R(wF2) = 14,17% for all 7400 re-flections. For [K(2,2,2-crypt)]2[HP7Cr(CO)3]: triklin, P 1,a = 12,000(3) AÊ , b = 14,795(3) AÊ , c = 17,421(4) AÊ , α = 93,01°,b = 93,79(2)°, c = 110,72(2)°, V = 2877(2) AÊ 3, Z = 2.

Introduction

Baudler and co-workers have developed the chemistryof the hydrogen polyphosphanes, HmPn where n > 1,over the past several years [1, 2]. Many of these com-pounds were first identified in decomposition bypro-ducts from distillations of diphosphane, P2H4. Becauseof their inherent instability, these species were charac-terized by spectroscopic means such as 31P NMR andmass spectrometry. Despite the size of this family of

* Correspondence Address:

Professor Bryan EichhornDepartment of ChemistryUniversity of MarylandCollege Park, MD 20742PHONE (3 01)4 05-18 64FAX (3 01)3 14-91 21b._eichhorn@umail.umd.edu

compounds [1], the only polycyclic hydrogen poly-phosphane isolated in pure form to date is hepta-phosphane-3, H3P7 (1). Compound 1 is best preparedfrom the mild methanolysis of (Me3Si)3P7 at low tem-peratures according to eq. (1) [3]. The structure of 1contains the well-known heptaphosphanortricyclaneP7 core and is formed

(Me3Si)3P7 + 3 MeOH40 C

H3P7 + 3 MeOSiMe3 (1)1

in two isomeric forms. Like the other hydrogen poly-phosphanes, 1 decomposes at room temperature togive higher order phosphanes and PH3.

In contrast to the instability of the hydrogen poly-phosphanes, the polyphosphide anions are stable andisolable [1, 4]. There are two general methods for thesynthesis of these compounds; namely, high tempera-ture reactions of phosphorus with alkali and alkalineearth metals [4±6] and low temperature P±P couplingreactions in solution. For example, the P7

3± ion (2) canbe generated in solution by nucleophilic cleavage ofP4 with LiPH2 as shown in eq. (2) [7]. Compound 2possesses the heptaphosphanortricyclane structurewhere the negative

3 P4 + 6 LiPH2 → 2 P73± + 6 Li+ + 4 PH3 (2)

2

charge is formally localized on the two-coordinatephosphorus atoms.

Baudler and co-workers first showed that 1 and 2could be interconverted in a stepwise fashion [8] byeither metallation of 1 with butyl lithium (eq. (3)) orprotolysis of 2 (eq. (4)) under modified stoichiometricconditions [9].

P7H3 + 3 Lin±Bu → Li3P7 + 3 butane (3)

Li3P7 + 3 H+ → P7H3 + 3 Li+ (4)

The intermediate species H2P7± and HP7

2± were spec-troscopically identified in these reactions [1, 2, 8].More recently, von Schnering and Korber isolated andstructurally characterized the H2P7

± ion as the PPh4+

salt [10].The heptaphosphide ion 2 is remarkably nucleophi-

lic in that it will de-alkylate NR4+ ions to give R2P7

±

ions (R = Me, Et, Bu, CH2Ph) in a stereospecific SN2

type reaction [11, 12]. Despite its potent nucleophili-city, 2 shows only modest Brùnsted basicity. Althoughthe Brùnsted basicity of 2 has not been quantified,protonation of the polyphosphides often requires rela-tively strong acids such as glacial acetic acid [1]whereas weaker acids such as MeOH are ineffective.The basicity of the polyphosphides can be enhancedthrough coordination of various transition metal com-plexes. For example, [P7W(CO)4]3± and [P7Ni(CO)]3±

are significantly more basic [13, 14] than P73± in that

the metallated compounds are protonated by MeOH

whereas protonation of 2 requires a stronger acid suchas NH4

+.In this paper, we describe two synthetic methods

for the preparation of the [HP7M(CO)3]2± ions fromthe [P7M(CO)3]3± precursors (M = Cr, W); namely, di-rect protonation and oxidation/radical hydrogen ab-straction. The latter reaction competes with oxidativeP±P coupling reactions and represents an unusual en-try into phosphane chemistry. In addition, the solidstate structures, qualitative pKa values, and solutiondynamics of the [HP7M(CO)3]2± ions as well as com-parative protonation and oxidation studies of P7

3± arealso described.

Results

Synthesis. Ethylenediamine solutions of [P7M(CO)3]3±,where M = Cr (3 a) or W (3 b), [15] react with weakacids with pKa's less than 18 to give [HP7M(CO)3]2± (4)compounds according to eq. (5). The complexes wereisolated as the dark red [K(2,2,2-crypt)]+ salts in ca.76% crystalline

[P7M(CO)3]3± + ªH+º → [HP7M(CO)3]2± (5)M = Cr (3 a) M = Cr (4 a)M = W (3 b) M = W (4 b)

yields and are moderately air and moisture sensitivein solution and the solid state. Eq. (5) chemistry alsooccurs in DMF and DMSO. 31P NMR studies showfast rates of reaction (t∞ ≈ 15 min) and virtually quan-titative conversions from 3 to 4 at ambient tempera-tures. Compounds 4 were characterized by IR, 1H, 13Cand 31P NMR spectroscopic studies, elemental ana-lyses and single crystal X-ray diffraction.

Compounds 3 are not protonated by MeOH and 4are efficiently deprotonated by MeO± in en or DMF(eq. (6)). In an attempt to establish an approximatepKa value for 4 b, protonation of 3 b with variousweak acids was attempted in DMSO [16, 17]. The re-sults are summarized in Table 1 and give a relativepKa range for 3 b in DMSO (pKDMSO) of 17.9 to 22.6.

[HP7M(CO)3]2± + MeO± en or DMF[P7M(CO)3]3± + MeOH (6)

4 3

Although fluorene (pKDMSO = 22.6) does not reactwith 3, 9-phenylfluorene (pKDMSO = 17.9) reactsquickly and is a convenient proton source for eq. (5)chemistry. Acids that would allow us to narrow thepKa range, such as 4-nitroaniline (pKDMSO = 21.0) and4-chloro-2-nitroaniline (pKDMSO = 18.9), appear tooxidize the clusters giving unidentified products.

Attempted room-temperature protonations of P73±

in the presence or absence of 2,2,2-crypt yield PH3

and other phosphanes when acids with pKDMSO ≤ 17.9are used as a proton source. These findings are inagreement with the low temperature protonationstudies of Baudler et al. [1]. With weaker acids

824 Z. anorg. allg. Chem. 624 (1998)

S. Charles et al., Protonation and Hydrogen Atom Abstraction Reactions 825

(pKDMSO ≥ 22.6), no reaction is observed after severaldays at room temperature.

Compounds 4 can be prepared by an alternativesynthetic route involving an initial oxidation of thecluster followed by a radical hydrogen atom abstrac-tion. DMSO, DMF or en/tol solutions of 3 react withone-half equiv of I2 in the presence of 2,2,2-crypt togive 4 according to eq. (7). In the presence of 2,2,2-crypt, the use of DMSO-d8, DMF-d7 or tol-d8 doesnot result in the incorporation of deuterium intothe final products, however, when the reaction isrun in DMSO-d8 in the absence of 2,2,2-crypt,[DP7W(CO)3]2± (d±4 b) is formed according to eq. (8).

[P7M(CO)3]3± + 1/2I2 + H´ → [HP7M(CO)3]2± + I± (7)3 4

[P7W(CO)3]3± + 1/2I2DMSO d8 [DP7W(CO)3]2± + I± (8)

3 b d±4 b

When [P7W(CO)3]3± is prepared in situ in DMF-d7

from the usual P73± and (mesitylene)W(CO)3 precur-

sors [15], I2 oxidation gives 4 b exclusively and d±4 b isnot detected by 31P NMR spectroscopy. The hydrogenatom source in this case is presumably the mesitylene.In the absence of a good hydrogen atom source, the I2

oxidations in DMSO and DMF give the known [18]ion [P5W(CO)3]± (5) as a prominent by-product.The results of the labeling studies are summarized inTable 2.

In the presence or absence of 2,2,2-crypt, P73± re-

acts with I2 to give P162± as the primary product [19]

along with other oxidation products. In the presenceof 2,2,2-crypt, the reactions are faster but the resultingproduct distributions are the same.

Structural Studies

The [HP7M(CO)3]2± ions (M = Cr, W) were structu-rally characterized by single crystal X-ray diffractionas their [K(2,2,2-crypt)]+ salts. An ORTEP drawing ofthe [HP7W(CO)3]2± anion (4 b) is shown in Figure 1.A summary of the crystallographic data is given inTable 3 and a listing of selected bond distances andangles for the [HP7W(CO)3]2± ion is given in Table 4.The refinement of the [HP7Cr(CO)3]2± structure washampered by weak X-ray data and the resulting me-tric parameters will therefore not be presented.

The [K(2,2,2-crypt)]+ salts of the [HP7M(CO)3]2±

ions are both triclinic, space group P 1, but are not iso-morphic. The [HP7M(CO)3]2± structure type containsa C3v M(CO)3 center and an g4-P7H group in whichthe hydrogen is attached to the P(1) atom. The hydro-gen atom was not crystallographically located butclearly resides on the P(1) atom as determined byspectroscopic studies (see below). The W±P bonddistances in 4 b (ave 2.620 AÊ ) are similar to thoseobserved for the [P7M(CO)3]3± ions [15] and arevirtually identical to those of [EtP7W(CO)3]2±

(2.629 AÊ ),[11] [(en)(CO)2WP7W(CO)3]3± (2.634 AÊ )[20] and related compounds (e. g., W(CO)4(P6Me6))[21]. The asymmetry observed for the P(4)±P(5) and

Table 1 Protonation Results in the Formation of 4 b and 2and pKDMSO. Values for Relevant Organic Acidsa), b)

Acid pKDMSO 3 b + acidc) 2 + acidc)

Acetic acid 11.9 4 b PH3 + dec9-Phenylfluorene 17.9 4 b PH3 + dec4-Chloro-2-nitroaniline 18.9 U U4-Nitroaniline 21.0 U UFluorene 22.6 N/R N/RAcetone 26.5 N/R N/RMethanol 29.1 N/R N/RWater 31.4 N/Rd) N/Rd)

Dimethylsulfoxide 35.1 N/R N/R

a) pKDMSO values taken from ref. [16] except those forwater and DMSO which came from ref. [17]. b) DMSO Solu-tion at 25 °C. c) N/R = no reaction, dec = unidentified decom-position products; U = unidentified product. d) Secondaryproducts appear after several hours.

Table 2 Results of Labeling Studies in the Formation of 4 b(eq. (7))

Solvent 2,2,2-crypt Resulta)

en/tol y 4 ben/tol-d8 y 4 ben/tol n decDMSO-d6 y 4 bDMSO-d6 n d±4 b (∼ 90%) + 5 (∼ 10%)b)

DMF-d7 y 4 bDMF-d7/mesitylene n 4 b (∼ 85%) + 5 (∼ 15%)b)

a) 4 b = [HP7W(CO)3]2±, d±4 b = [DP7W(CO)3]2±, dec = un-identified decomposition products, 5 = [P5W(CO)3]±, seeref. [18]. b) Percentages were estimated from 31P NMR ana-lysis.

Fig. 1 ORTEP drawing of the [HP7W(CO)3]2± ion, 4 b,using the common atomic numbering scheme. The hydrogenwas not crystallographically located.

P(6)±P(7) separations (2.968(4) AÊ and 3.307(4) AÊ , re-spectively) are also typical for these types of com-pounds [11, 14, 15, 20, 22, 23] but are larger than thesame asymmetries in [P7Cr(CO)3]3± [15]. The largerdistortion in the present compound presumably re-sults from the larger size of W relative to Cr.

The effect of the proton on the P7 cage can be seenby comparing the structure with [P7Cr(CO)3]3± andrelated compounds [15, 23]. The P(1)±P(2) andP(1)±P(3) bonds are approximately 0.04 AÊ longer thancorresponding bonds in [P7Cr(CO)3]3± [15] whereasthe other P±P bonds are 0.02 to 0.04 AÊ shorter. Thiseffect is similar to those seen for the alkylated and

protonated P73± compounds [10]. The [K(2,2,2-crypt)]+

ions were crystallographically well behaved and werewell separated from the anions.

Spectroscopic Studies

The 1H NMR spectrum for 4 a shows a P±H resonanceat 4.8 ppm (d = 4.2 ppm for 4 b) which is a doublet ofmultiplets with 1J31P±1H = 168 Hz (see Figure 2). Thecarbonyl carbon resonances appear at 242 ppm (4 a)and 228 ppm (4 b) in their respective 13C NMR spec-tra. Both resonances show broadening due tounresolved coupling to phosphorus and 4 b displays1J13C±183W satellites of 179 Hz. The chemical shifts areca. 4 ppm upfield of the unprotonated analogs 3 a and3 b [15].

The 31P NMR spectrum for 4 a is shown in Figure 3and is virtually identical to that of 4 b. On the basis ofthe solid-state structures, seven phosphorus reso-nances would be anticipated due to the seven inequi-valent phosphorus atoms. However, the 31P NMRspectra for 4 show AA'BB'MM'X spin patterns withfour resonances in 2 : 2 : 2 : 1 integral ratios. The fourpeaks correspond to the two equivalent pairs of phos-phorus atoms bound to the transition metal, P(4), P(6)and P(5), P(7), the two bridging phosphorus atomsP(2) and P(3), and the protonated phosphorus atomP(1), respectively. The asymmetries in the P(4)±P(5)/P(6)±P(7) separations observed in the solid state aretime averaged in solution due to an intramolecularwagging process that is common to all members of thegeneral class of compounds [11, 15, 20]. The com-pounds remain fluxional at ±60 °C in DMF-d7. The ex-

826 Z. anorg. allg. Chem. 624 (1998)

Table 3 Crystallographic data for[K(2,2,2-crypt)]2[HP7M(CO)3] (M = Cr, W)

formula C39H73N4O15K2P7Cr C39H73N4O15K2P7Wfw 1185.0 1316.9space group P 1 P 1a, AÊ 12.000(3) 10.9709(8)b, AÊ 14.795(3) 13.9116(10)c, AÊ 17.421(4) 19.6400(14)α, deg 93.01(2) 92.435(6)b, deg 93.79(2) 93.856(6)c, deg 110.72(2) 108.413(6)V, AÊ 3 2877(2) (Z = 2) 2831.2(4) (Z = 2)D(calcd), g cm3 1.37 1.544l(MoKα), cm±1

(k = 0.71073 AÊ )24.46

temp, K 296 153(2)2 h (max), deg 45.0F(000) 1342no. of reflns, colld 7868no. of ind. reflns 7400 [Rint = 0.0344]Data/restraints/parameters

7400/136/657

Fo ≥ 4r(Fo) 5733 dataR(F), %a) 5.20Rw(F2), %b) 12.67

D/r(max) ≤ 0.001GOF 1.049

a) R(F) = R|Fo ± Fc|/RFo. b) Rw(F2) = (Rw|Fo ± Fc|2/RwFo

2)1/2.

Table 4 Selected bond distances (AÊ ) and angles (°) for the[HP7W(CO)3]2± ion

P(1)±P(2) 2.163(4) P(1)±P(3) 2.162(4)P(2)±P(4) 2.219(4) P(2)±P(5) 2.217(4)P(3)±P(6) 2.220(4) P(3)±P(7) 2.199(4)P(4)±P(5) 2.968(4) P(6)±P(7) 3.307(4)P(4)±P(6) 2.145(4) P(5)±P(7) 2.162(4)P(4)±W 2.565(3) P(5)±W 2.563(2)P(6)±W 2.674(3) P(7)±W 2.676(3)W±C(1) 1.971(10) W±C(2) 1.944(12)W±C(3) 1.975(11) C(1)±O(1) 1.153(11)C(2)±O(2) 1.184(13) C(3)±O(3) 1.164(11)

P(1)±P(2)±P(4) 106.(2) P(1)±P(3)±P(7) 97.8(2)P(2)±P(1)±P(3) 100.0(2) P(2)±P(4)±P(6) 105.9(2)P(3)±P(7)±P(5) 103.74(14) P(4)±P(2)±P(5) 83.99(13)P(6)±P(3)±P(7) 96.9(2) P(4)±W±P(5) 70.73(8)P(4)±W±P(6) 48.28(9) P(6)±W±P(7) 76.36(9)P(2)±P(4)±W 101.65(12) P(3)±P(7)±W 93.52(11)P(4)±P(6)±W 63.20(10) P(7)±P(5)±W 68.38(10)P(4)±W±C(1) 129.2(3) P(5)±W±C(1) 136.9(3)P(4)±W±C(2) 84.2(3) P(4)±W±C(3) 133.1(3)P(6)±W±C(3) 175.9(3) P(7)±W±C(2) 176.9(3)

Fig. 2 The P±H resonance of the 1H NMR spectrum of[HP7Cr(CO)3]2±, 4 a, recorded at 27 °C at 200.1 MHz inDMF-d7 solution.

Fig. 3 31P NMR spectrum for [HP7Cr(CO)3]2±, 4 a, re-corded at 27 °C and 81.0 MHz from DMF-d7 solution.

S. Charles et al., Protonation and Hydrogen Atom Abstraction Reactions 827

change process generates a virtual mirror plane thatbisects the P(4)±P(6) and P(5)±P(7) bonds and makesatoms P(4) and P(5) chemically equivalent to atomsP(6) and P(7), respectively. However, inversion atP(1) is not observed on the NMR time scale. The me-chanism of exchange is attributed to an intramolecu-lar wagging process based on the following considera-tions: 1) rapid inversion at P(1) without the waggingprocess would render P(2) and P(3) inequivalent,which is not observed, and 2) rapid wagging and inver-sion at P(1) would make P(4), P(5), P(6), and P(7) allchemically equivalent, which is also not observed.

The calculated and observed, coupled and de-coupled 31P NMR P(1) resonances for 4 b and d±4 bare shown in Figure 4. The proton-coupled spectra re-veal P±H couplings identical to those observed in the1H NMR spectra. The P±D coupling constant of thedeuterated compound is the expected 15.4% of theobserved P±H coupling constant [24].

The IR spectra for 4 contain two m(HP) bands be-tween 2235 and 2210 cm±1 and three m(CO) bands be-tween 1892 and 1755 cm±1. The carbonyl stretching vi-brations are blue shifted by ca. 40 cm±1 from theparent ions 3 due to the decrease in negative charge[15].

Discussion

Baudler and co-workers have shown that, with theexception of H3P7, the polycyclic hydrogen poly-phosphanes are unstable and can only be studied byspectroscopic means [1]. Moreover, H3P7 is onlymoderately stable [25] and decomposes on warming toroom temperature which contrasts the chemistry ofthe alkylated R3P7 analogs [26±28]. This inherent in-stability makes systematic studies of the solution

chemistry difficult. Korber and von Schnering have re-cently isolated and structurally characterized theH2P7

± ion [10] which is consistent with the enhancedstability of the anionic polyphosphides relative to theneutral polyphosphanes [1, 2]. We find that the anio-nic metallated hydrogen polyphosphides are relativelyrobust which allows for study of the structural and so-lution chemistry [11, 13±15]. Comparative protonationstudies show that P7

3± and the [P7M(CO)3]3± com-plexes (M = Cr, W) have similar nucleophilicities (i. e.reactions with NR4

+ salts) and Brùnsted basicities (i. e.the conjugate acids have 17.9 < pKDMSO < 22) whereasthe tetracarbonyl compounds [P7M(CO)4]3± (M = Mo,W) [13] and the nickel complex [P7Ni(CO)]3± [14]show enhanced Brùnsted basicity (i. e. the conjugateacids have pKDMSO < 29.1).

The reactions between I2 and the [P7M(CO)3]3±

complexes (eq. (7)) were designed to oxidatively cou-ple two clusters together to form [P14M2(CO)6]4± com-plexes. The targeted complexes would contain two[P7M(CO)3] units linked by a P±P bond between theP(1) atoms. Fenske and co-workers have successfullyaccomplished such a coupling using Li3P7 andNiCl2(PBu3)2 which gives [{Ni(PBu3)2}4P14] withthe aforementioned P14 unit [29]. However, with thenon-coordinating oxidant I2, the transient radical[´ P7M(CO)3]2± abstracts a hydrogen from either thesolvent, the [K(2,2,2-crypt)]+ counterions, or other hy-drogen atom sources. Although we have not been ableto detect the radical by electrochemical ± epr meth-ods, its presence is confirmed by the labeling studiesdescribed earlier. These data suggest that the[´ P7M(CO)3]2± radicals generated in the oxidationprocess (eq. (7)) are too reactive in solution to under-go simple P±P coupling reactions. The instability ofthe [´ P7M(CO)3]2± radical is also consistent withits fragmentation (decomposition) to give the[P5M(CO)3]± complex (5) in the absence of good hy-drogen atom sources.

Experimental Section

General Data

General operating procedures used in our laboratory havebeen described elsewhere [15]. Proton (1H) NMR spectrawere recorded at ambient temperature on both Bru-ker WP200 (200.133 MHz) and AM400 (400.136 MHz) spec-trometers. Elemental analyses were performed under inertatmosphere by Schwarzkopf Microanalytical Laboratories,Woodside, N.Y. and Desert Analytics, Tucson, AZ. Fluorene,9-phenylfluorene, 4-chloro-2-nitroaniline, and 4-nitroanilinewere purchased from Aldrich and used without further puri-fication. DMF was purchased from Burdick & Jackson (HighPurity) and distilled at reduced pressure from K4Sn9. Thesynthesis of the [K(2,2,2-crypt)]3[P7M(CO)3] compoundswere reported previously [15].

Fig. 4 Calculated (top) and observed (bottom) 31P NMRspectral P(1) resonances for the following compounds underthe following conditions: a) proton coupled 31P NMR spec-trum for 4 b, b) proton decoupled 31P NMR spectrum for 4 b,c) proton coupled 31P NMR spectrum for d±4 b. The aster-isks denotes an impurity.

Synthesis

Preparation of [K(2,2,2-crypt)]2[HP7Cr(CO)3]. K3P7 (29.6 mg,0.089 mmol), 2,2,2-crypt (100.0 mg, 0.27 mmol) and (mesity-lene)Cr(CO)3 (22.4 mg, 0.089 mmol) were dissolved in en(∼ 3 mL) in a dry box and stirred for 12 h. After 12 h, the re-sulting orange solution was analyzed by 31P NMR to confirmthe formation of 3 a. 9-Phenylfluorene (21.6 mg, 0.089 mmol)was added as a solid and the reaction mixture was stirred foran additional 2 h producing a dark red solution. The reactionmixture was filtered through ca. one quarter in. of tightlypacked glass wool in a pipette. After 4 h, the reaction vesselcontained rectangular dark red crystals that were removedfrom the mother liquor, washed with toluene, and dried undervacuum (crystalline yield, 80 mg, 76%). Anal. Calcd. forC39H73N4O15K2P7Cr: C, 39.53; H, 6.21; N, 4.73%. Found: C,39.78; H, 6.21; N, 4.83%. IR (KBr pellet), cm±1: 2219, 2210,1872, 1799, 1755. 1H NMR (DMF-d7) d(ppm): 4.8 (dm,1JH±P = 168 Hz). 13C NMR (DMF-d7) d(ppm): 242 (br s,CO). 31P{1H} NMR (DMF-d7) d(ppm): 119 [ttt, 1JP±P =270 Hz, 2JP±P = 27 Hz, 2JP±P = 7.5 Hz; 1 P, P(1)], ±20 [2nd or-der multiplet, 2 P, P(2,3)], ±127 [2nd order multiplet, 2 P,P(4,6) or P(5,7)], ±153 [2nd order multiplet, 2 P, P(4,6) orP(5,7)].

Preparation of [K(2,2,2-crypt)]2[HP7W(CO)3]. A procedureidentical to that described for [K(2,2,2-crypt)]2[HP7Cr(CO)3]was followed except (mesitylene)W(CO)3 (34.4 mg,0.089 mmol) was used in the reaction. Dark red crystals ofthe title compound were removed from the mother liquor,washed with toluene, and dried under vacuum (crystallineyield, 89 mg, 76%). Anal. Calcd. for C39H73N4O15K2P7W: C,35.57; H, 5.59; N, 4.25%. Found: C, 35.94; H, 5.59; N, 4.48%.IR (KBr pellet), cm±1: 2235, 2212, 1880, 1800, 1758.1H NMR (DMF-d7) d(ppm): 4.2 (dm, 1JH±P = 172 Hz).13C NMR (DMF-d7) d(ppm): 228 (br s, 1JC±W = 179 Hz, CO).31P{1H} NMR (DMF-d7) d(ppm): 111 [tt, 1JP±P = 263 Hz,2JP±P = 29 Hz, 1 P, P(1)], 24 [2nd order multiplet, 2 P, P(2,3)],±149 [2nd order multiplet, 2 P, P(4,6) or P(5,7)], ±181 [2nd or-der multiplet, 2 P, P(4,6) or P(5,7)].

pKa-Determination Experiments

In a dry box K3P7 (29.6 mg, 0.089 mmol) and (mesity-lene)W(CO)3 (34.4 mg, 0.089 mmol) were combined inDMSO-d6 (∼ 2 mL) and stirred for 12 h yielding a dark redsolution. Fluorene (14.8 mg, 0.089 mmol) or 9-phenylfluor-ene (21.6 mg, 0.089 mmol) was added as a solid. The reac-tion mixture was stirred for an additional 1/2 h. An aliquotwas removed from each reaction mixture and analyzed by31P NMR spectroscopy.

Labeling Studies with crypt

Solid [K(2,2,2-crypt)]3[P7W(CO)3] (115 mg, 0.064 mmol) wasprepared as previously described [15] and then dissolved inDMSO-d6 (0.75 mL). A DMSO-d6 solution of I2 (8.5 mg,0.033 mmol) was slowly added to the previous solution andthe mixture stirred for ca. 10 min. The solution was thentransferred to a NMR tube and the reaction analyzed by31P NMR spectroscopy.

31P{1H} NMR (DMSO-d6) d(ppm): 114 [tt, 1JP±P =262 Hz], 25 [2nd order multiplet, 2 P, P(2,3)], ±150 [2nd or-der multiplet, 2 P, P(2,3)], ±178 [[2nd order multiplet, 2 P,

P(2,3)]. A procedure identical to that described above wasfollowed for all the labeling studies with crypt.

Labeling studies without crypt

[P7W(CO)3]3± was prepared by stirring K3P7 (30 mg,0.089 mmol) and (mesitylene)W(CO)3 (35 mg, 0.90 mol) inen at room temperature for 18 h. An aliquot of this solutionwas analyzed by 31P NMR to ensure formation of 3 a. Thesolution was evaporated to dryness and the residue ex-tracted into DMSO-d6. To this solution was added I2

(11.5 mg, 0.045 mmol) dissolved in DMSO-d6 and the reac-tion mixture stirred for ca. 10 min. The solution was thentransferred to a NMR tube and the reaction analyzed by31P NMR spectroscopy.

31P{1H} (DMSO-d6) d(ppm): 113.5 [tt, 1JP±P = 260], 25[2nd order multiplet, 2 P, P(2,3)], ±148 [2nd order multiplet,2 P, P(2,3)], ±178 [[2nd order multiplet, 2 P, P(2,3)]. A proce-dure identical to that described above was followed for allthe labeling studies without crypt.

Reaction of K3P7 with I2

K3P7 (30 mg, 0.089 mmol) and 2,2,2-crypt (100.0 mg,0.27 mmol) were dissolved in DMF (ca. 3 mL) in a dry box.I2 (11.5 mg, 0.045 mmol) dissolved in DMF was slowly addedto this solution and the reaction mixture stirred for 3 hrsproducing a dark red colored solution. An aliquot of the so-lution was used for 31P NMR studies. An identical reactionwas conducted in the absence of 2,2,2-crypt.

Crystallographic Experimental Detailsfor [K(2,2,2-crypt)]2[HP7W(CO)3].

A red parallelepiped with dimensions 0.50 × 0.18 × 0.10 mmwas placed on the Enraf-Nonius CAD-4 diffractometer. Thecrystals' final cell parameters and crystal orientation matrixwere determined from 25 reflections in the range13.8 < h < 18.6°; these constants were confirmed with axialphotographs. Data were collected [MoKα] with x : 2 h scansover the range 2.3 < h < 22.5°. Seven w-scan reflections werecollected over the range 7.9 < h < 13.°; the absorption correc-tion was applied with transmission factors ranging from0.0143±0.0357.

Data were corrected for Lorentz and polarization factorsand reduced to F2

o and r (F2o) using the program XCAD4.

The structure was determined by direct methods (XS inSHELXTL) with the successful location of the tungsten, sev-en phosphorus, and two potassium heavy atoms. One subse-quent difference-Fourier map revealed the location of sev-eral atoms comprising the two cryptand ions and these peakpositions were used to fit an idealized cryptand molecule.Both cryptand ions are chemically identical and were there-fore refined using SAME instructions throughout the refine-ment process. A further difference-Fourier map revealed arather large peak, originally believed to be a `ghost' peak,nearly 7.0 eAÊ ±3 in height within the P7 framework. Uponfurther analysis, this peak and several of its associates weredetermined to be the rotated model of the WP7(CO)3 com-plex originally found. An orthogonalized model was createdfor the main WP7(CO)3 molecule and was used to fit the ex-isting peaks and thereby create an optimized model basedupon the current locations of those peaks present. This mod-

828 Z. anorg. allg. Chem. 624 (1998)

S. Charles et al., Protonation and Hydrogen Atom Abstraction Reactions 829

el was refined using SAME instructions. The occupancies ofthe major and minor contributors were refined with the re-sult major : minor, 0.9589 : 0.0411. In addition, since they over-all occupancy of the minor contributor was so small, nearlynegligible, the atoms of the minor contributor were refinedisotropically with their thermal parameters fixed equal tothe tungsten atom, W(1 A). Hydrogen atoms were placed incalculated positions with d(C±H2) = 0.990 AÊ and UH beingset equal to 1.2U(parent). The structure was refined to conver-gence [D/r ≤ 0.001] with all non-hydrogen atoms anisotropic,with R(F) = 7.65%, wR(F2) = 14.17% and GOF = 1.049 forall 7400 unique reflections [R(F) = 5.20%, wR(F2) = 12.67%for those 5733 data with Fo > 4r(Fo)]. A final difference-Fourier map possessed a set of highest peaks in the vicinityof either W(1) or W(1 A) with |Dq| ≤ 1.31 eAÊ ±3, the largestother spurious peaks had |Dq| ≤ 0.99 eAÊ ±3.

Acknowledgment. This work was funded by the NationalScience Foundation through Grant CHE-9500686.

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